Absorbent articles (disposable diapers, etc.) using water-absorbing resin particles are usually produced by fixing water-absorbing resin to a matrix composed of cellulose fibers uniformly and packing them with organic synthetic fiber such as non-woven fabric. In practical use, however, water-absorbing resin particles are shed or moved easily by vibration to generate deviation of particles in absorbers. As a result, efficient diffusion of an absorbate such as urine is disturbed, so that such problems as urine leakage and developing a rash have been caused.
In recent years, needs for reduction in thickness of absorbent articles such as disposable diapers have continued to evolve and the trend toward pulp-free has increasingly been advancing. That is, the ratio of the pulp serving as a matrix in the absorber relative to the water-absorbing resin particles has become less than before, and therefore the fixation of water-absorbing resin particles in an absorber has become more difficult and, for example, such problems as urine leakage and developing a rash tend to occur more easily than before. From such a point of view, there has been demanded a technology to fix water-absorbing resin particles to pulp fiber or other fibrous base materials efficiently.
As attempts for solving the above problems, there are known (1) a method in which a pressure-sensitive adhesive is applied to the surface of a fibrous base material and then water-absorbing resin particles are adhered, and (2) a method in which water-absorbing resin particles are dispersed in an organic solvent in which a binder has been dissolved, then the dispersion is applied to or included in a fibrous base material, followed by heating and drying, thereby vaporizing the organic solvent and achieving fixation. However, the method (1) has a problem that deterioration in absorber performance or handling nature are invited because the fibrous base material itself is adhered by a pressure-sensitive adhesive which does not take part in adhesion between the water-absorbing resin particles and the fibrous base material. In the method (2), the process of heating, drying and vaporizing the organic solvent is complicated and requires increased costs and there is an apprehension regarding the safety of residual organic solvent.
In addition, a new method known in the art is a method of fixing water-absorbing resin particles to a fibrous base material by coating the surface of the water-absorbing resin particles beforehand with heat-weldable resin such as polyolefin resin, e.g., polyethylene wax, polyolefin derivatives modified with acid anhydrides or the like, polyester resin, polyamide resin, and polystyrene resin, or by mixing such heat-weldable resin with water-absorbing resin particles and then heat-welding them.